Antihydrogen formation at AEgIS at CERN leverages charge exchange between Rydberg positronium (Ps*) and antiprotons, with cross-sections scaling with the Ps principal quantum number $n^4$ and inversely with relative velocity $𝑣^{−2}$. However, the motional Stark effect and velocity mismatch between Ps and antiprotons impose stringent constraints, limiting efficiency. Advances in transmission positronium converters mitigate self-ionization losses and improve velocity alignment, promising a significant boost in antihydrogen yield. This work evaluates formation cross-sections, Ps velocity profiles, and the integration of advanced transmission Ps converters for precision gravitational studies.

Primary goal of the AEḡIS experiment is to precisely measure the free fall of antihydrogen within Earth’s gravitational field. To this end, cold (≈50 K) antihydrogen will traverse a two-grid moiré deflectometer before annihilating onto a position-sensitive detector, which shall determine the vertical position of the annihilation vertex relative to the grids with micrometric accuracy. Here, we introduce a vertexing detector based on a modified mobile camera sensor and experimentally demonstrate that it can measure the position of antiproton annihilations within 0.62 − 0.22 + 0.40 μm, a 35-fold improvement over the previous state of the art for real-time antiproton vertexing. These methods are directly applicable to antihydrogen. Moreover, the sensitivity to light of the sensor enables in situ calibration of the moiré deflectometer, substantially reducing systematic errors. This sensor emerges as a breakthrough technology toward the AEḡIS scientific goals and will constitute the basis for the development of a large-area detector for conducting antihydrogen gravity measurements.

A new bunched positron (e + ) beam is currently under final development at the AntiMatter Laboratory (AML) of the University of Trento. The positron beam has been designed to deliver bunches containing up to a few 10 5 positrons compressed to durations of less than 2 ns and with a tunable energy range between 1 and 21 keV. Thanks to the specifications of this new apparatus, different experiments based on the production of positronium (Ps) in nanostructured e + /Ps converters have been planned. A silicon target with nanochannels connected to laser-written buried micro-cavities is under development. The intent is to produce Ps atoms in the nanochannels and collect them in the micro-cavities to explore the mechanisms of Ps/cavity walls interaction and Ps/Ps interaction. Moreover, Ps clouds emitted into vacuum after implantation of e + bunches in nanochanneled e + /Ps converters will be employed to perform measurements of the entanglement of the three annihilation gamma-rays of Ps and the inertial sensing on Ps. In this work, the characteristics of the new positron beam at the AML of Trento will be presented and the scheduled experiments will be illustrated.

The experimental demonstration of positronium laser cooling with stationary broadband laser pulses with negative detuning is briefly described. Considerations on the limits of the current experiment and possible future developments follow. In particular, the benefit of positron remoderation, use of a magnetic field, positronium polarization, pulse shaping, coherent laser cooling and deceleration are shortly discussed.

We report on a Q-switched alexandrite based- 100 ns long pulse duration ultra-violet laser system. The central wavelength of the fundamental pulse is set by a Volume Bragg Grating in reflection and can be tuned between 728 nm and 742 nm. The spectral bandwidth is- 130 GHz. This laser system was designed in view of Doppler cooling of a cloud of a near room temperature positronium by strongly saturating the 1 3 S- 2 3 P transition. In addition, we report on the development of a KD*P Pockels cell driver designed to both Q-switch the cavity and induce a sharp falling edge of the laser pulse so that the end of the positronium-laser interaction time can be controlled with nanosecond precision.

Studies based on imaging the annihilation of the electron (e$^{-}$) and its antiparticle positron (e$^{+}$) open up several interesting applications in nuclear medicine and fundamental research. The annihilation process involves both the direct conversion of e$^{+}$e$^{-}$ into photons and the formation of their atomically bound state, the positronium atom (Ps), which can be used as a probe for fundamental studies. With the ability to produce large quantities of Ps, manipulate them in long-lived Ps states, and image their annihilations after a free fall or after passing through atomic interferometers, this purely leptonic antimatter system can be used to perform inertial sensing studies in view of a direct test of Einstein equivalence principle. It is envisioned that modular multistrip detectors can be exploited as potential detection units for this kind of studies. In this work, we report the results of the first feasibility study performed on a e$^{+}$ beamline using two detection modules to evaluate their reconstruction performance and spatial resolution for imaging e$^{+}$e$^{-}$ annihilations and thus their applicability for gravitational studies of Ps.

A powerful and robust control system is a crucial, often neglected, pillar of any modern, complex physics experiment that requires the management of a multitude of different devices and their precise time synchronisation. The AEḡIS collaboration presents CIRCUS, a novel, autonomous control system optimised for time-critical experiments such as those at CERN’s Antiproton Decelerator and, more broadly, in atomic and quantum physics research. Its setup is based on Sinara/ARTIQ and TALOS, integrating the ALPACA analysis pipeline, the last two developed entirely in AEḡIS. It is suitable for strict synchronicity requirements and repeatable, automated operation of experiments, culminating in autonomous parameter optimisation via feedback from real-time data analysis. CIRCUS has been successfully deployed and tested in AEḡIS; being experiment-agnostic and released open-source, other experiments can leverage its capabilities.

We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 1^{3}S-2^{3}P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 2^{3}P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud's temperature from 380(20) to 170(20) K. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v_{1D}<3.7×10^{4}  ms^{-1}.

We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 13S−23P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 23P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud’s temperature from 380(20) to 170(20) K. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v1D<3.7×104 ms−1. Published by the American Physical Society 2024

Modern physics experiments are frequently very complex, relying on multiple simultaneous events to happen in order to obtain the desired result. The experiment control system plays a central role in orchestrating the measurement setup: However, its development is often treated as secondary with respect to the hardware, its importance becoming evident only during the operational phase. Therefore, the AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) collaboration has created a framework for easily coding control systems, specifically targeting atomic, quantum, and antimatter experiments. This framework, called Total Automation of LabVIEW Operations for Science (TALOS), unifies all the machines of the experiment in a single entity, thus enabling complex high-level decisions to be taken, and it is constituted by separate modules, called MicroServices, that run concurrently and asynchronously. This enhances the stability and reproducibility of the system while allowing for continuous integration and testing while the control system is running. The system demonstrated high stability and reproducibility, running completely unsupervised during the night and weekends of the data-taking campaigns. The results demonstrate the suitability of TALOS to manage an entire physics experiment in full autonomy: being open-source, experiments other than the AEgIS experiment can benefit from it.

At the AntiMatter Laboratory in Trento, a new setup to produce intense bunches of positrons with a time duration of 2.5 ns and positron kinetic energy from 0.5 to 15 keV is under commissioning. The apparatus is designed for carrying out two main fundamental quantum experiments, i.e., the study of entanglement of three positronium annihilation gammas and the measurements of accelerations of positronium (including gravitational acceleration). In addition to the bunched beam, production of positronium in vacuum and its excitation in long-lived states will be necessary. Based on the acquired know-how of the AntiMatter Laboratory, the design of the experiments will be described

Hydrothermal treatments of soda-lime silicate glass cause a remarkable improvement in the resistance to flaw formation with an increase of the critical load to approximate to 1 kgf. This remarkable effect is achieved even if the reaction layer between the glass and water solution is well below 1 mu m. Positron Doppler broadening spectroscopy (DBS) reveals that the hydrothermal treatment causes a drop in the free volume of the glass network near the surface connected with the diffusion of molecular water whose presence was further confirmed by Fourier transformed infrared (FTIR) spectroscopy and secondary ion mass spectrometry (SIMS). Based on FTIR and SIMS, we also argue that the hydrothermal ion exchange is a double-step process: first H+ substitutes Na+ in the network, and following molecular water permeates the system. Moreover, we show that the presence of water in the network is fundamental in stabilizing the modified glass surface leading to toughening. Once molecular water is released, the network is quickly polymerized and becomes more brittle. Hydrothermal toughening is only a partially reversible process, once water is released it is not possible to reobtain the same properties with a second treatment. Finally, it is shown that air and tin side of the float glass perform differently as a result of different water diffusion kinetics related to dissimilarities in the network density. Hydrothermal treatments of soda-lime silicate glass allow for a substantial toughening of the material. Molecular water diffuses within the glass structure and leads to substantial densification of the network detected by antimatter probe. The water diffusion on the tin side of the float glass is slower leading to a reduced resistance to the crack formation. image

In this work we report on the systematic characterization of a rare -gas moderated magnetically-transported continuous positron beam based on a 22Na radioactive source. The characterization was performed with three different rare -gas solid moderators: Ne, Ar, and Kr. Each moderator was deposited and then thermal annealed at temperature - 35 % and - 30 % lower than the melting point, respectively. Tests of moderation/magnetic transport efficiency of the apparatus have shown a maximum efficiency of 1.8 10-3, 2.0 10-3 and 0.6 10-3 for Ne, Ar, and Kr, respectively. The average longitudinal kinetic energy of positrons was found to be - 0.95 eV, -1.25 eV, and - 0.45 eV for Ne, Ar, and Kr moderator, respectively. The spin polarization measurement of moderated positrons was performed by using the Doppler broadening of the annihilation gamma-rays from positronium formed in oxidized nanochanneled silicon positron/positronium converters. Polarization values of 0.30 +/- 0.01, 0.29 +/- 0.01 and 0.29 +/- 0.01 were found for Ne, Ar, and Kr moderator, respectively.

Three Positron Annihilation Spectroscopy (PAS) techniques have been employed to investigate the point defects of Al-doped Zinc Oxide (AZO) thin films grown by Radio Frequency (RF) magnetron sputtering with different substrates and deposition parameters. The films were grown with thickness varying from 100 to 300 nm, and their crystalline quality ranged from single crystalline epitaxial to partially amorphous. We found that the main defect in the crystalline samples is the 3VZn−VO four vacancy complex, with a concentration around 1018−1019 cm−3. In polycrystalline films larger vacancy clusters, within 10%−20% of the total concentration, were detected. These vacancy clusters are inferred to be most likely located at the grain boundaries. In partially amorphous films the concentration of these larger vacancy clusters, located either at grain boundaries or in the amorphous regions of the film, approached even the 40%, and also some sub-nano voids have been observed.

The primary goal of the AEgIS experiment is to precisely measure the free fall of antihydrogen within Earth's gravitational field. To this end, a cold  50K antihydrogen beam has to pass through two grids forming a moiré deflectometer before annihilating onto a position-sensitive detector, which shall determine the vertical position of the annihilation vertex relative to the grids with micrometric accuracy. Here we introduce a vertexing detector based on a modified mobile camera sensor and experimentally demonstrate that it can measure the position of antiproton annihilations with an accuracy of 0.62^+0.40_-0.22μ m, which represents a 35-fold improvement over the previous state-of-the-art for real-time antiproton vertexing. Importantly, these antiproton detection methods are directly applicable to antihydrogen. Moreover, the sensitivity to light of the sensor enables the in-situ calibration of the moiré deflectometer, significantly reducing systematic errors. This sensor emerges as a breakthrough technology for achieving the scientific goals and has been selected as the basis for the development of a large-area detector for conducting antihydrogen gravity measurements.

Low-temperature antihydrogen atoms are an effective tool to probe the validity of the fundamental laws of Physics, for example the Weak Equivalence Principle (WEP) for antimatter, and -generally speaking- it is obvious that colder atoms will increase the level of precision. After the first production of cold antihydrogen in 2002 [1], experimental efforts have substantially progressed, with really competitive results already reached by adapting to cold antiatoms some well-known techniques pre- viously developed for ordinary atoms. Unfortunately, the number of antihydrogen atoms that can be produced in dedicated experiments is many orders of magnitude smaller than of hydrogen atoms, so the development of novel techniques to enhance the production of antihydrogen with well defined (and possibly controlled) conditions is essential to improve the sensitivity. We present here some experimental results achieved by the AEgIS Collaboration, based at the CERN AD (Antiproton Decelerator) on the production of antihydrogen in a pulsed mode where the production time of 90% of atoms is known with an uncertainty of ~ 250 ns [2]. The pulsed antihydrogen source is generated by the charge-exchange reaction between Rydberg positronium (Ps*) and an antiproton (p¯): p¯ + Ps* → H¯* + e−, where Ps* is produced via the implantation of a pulsed positron beam into a mesoporous silica target, and excited by two consecutive laser pulses, and antiprotons are trapped, cooled and manipulated in Penning-Malmberg traps. The pulsed production (which is a major milestone for AEgIS) makes it possible to select the antihydrogen axial temperature and opens the door for the tuning of the antihydrogen Rydberg states, their de-excitation by pulsed lasers and the manipulation through electric field gradients. In this paper, we present the results achieved by AEgIS in 2018, just before the Long Shutdown 2 (LS2), as well as some of the ongoing improvements to the system, aimed at exploiting the lower energy antiproton beam from ELENA [3].

The J-PET detector, which consists of inexpensive plastic scintillators, has demonstrated its potential in the study of fundamental physics. In recent years, a prototype with 192 plastic scintillators arranged in 3 layers has been optimized for the study of positronium decays. This allows performing precision tests of discrete symmetries (C, P, T) in the decays of positronium atoms. Moreover, thanks to the possibility of measuring the polarization direction of the photon based on Compton scattering, the predicted entanglement between the linear polarization of annihilation photons in positronium decays can also be studied. Recently, a new J-PET prototype was commissioned, based on a modular design of detection units. Each module consists of 13 plastic scintillators and can be used as a stand-alone, compact and portable detection unit. In this paper, the main features of the J-PET detector, the modular prototype and their applications for possible studies with positron and positronium beams are discussed. Preliminary results of the first test experiment performed on two detection units in the continuous positron beam recently developed at the Antimatter Laboratory (AML) of Trento are also reported.

Advanced spectroscopy experiments and new physics experiments with positronium atoms in vacuum will benefit from positronium production in an environment free of magnetic and electrostatic fields. Here, we present a novel scheme for generating a bunched positron beam. The positron bunches are prebunched before extraction from a buffer-gas trap, nonadiabatically extracted from a 700 G magnetic field, energy elevated up to 20 kV, and bunched on a target in a free field. According to simulations of the system, 60% of cooled positrons in the buffer-gas trap are extracted and focused on the target in a time spread of 2.5 ns full width tenth maximum (FWTM) and a spot of about 4 mm FWTM for positron implantation energy higher than 3 keV. These performance numbers are achieved in the same apparatus through a combination of several innovative beam manipulations.

We describe a novel method to use a scintillating fiber detector similar to the Fast Annihilation Cryogenic Tracking (FACT) used at the antimatter experiment AEḡIS to monitor the presence of ortho-positronium. A single scintillating fiber was coupled to a photomultiplier tube and irradiated by flashes of about 6 × 106 gamma quanta with 511 keV energy, produced by approximately 10 ns long positron pulses. The results were used to demonstrate the ability to track the creation and annihilation of ortho-positronium atoms over time in cryogenic and highly magnetic environments by using the FACT detector as a "digital calorimeter".

We present a hybrid imaging/timing detector for force sensitive inertial measurements designed for measurements on positronium, the metastable bound state of an electron and a positron, but also suitable for applications involving other low intensity, low energy beams of neutral (antimatter)-atoms, such as antihydrogen. The performance of the prototype detector was evaluated with a tunable low energy positron beam, resulting in a spatial resolution of approximate to <i 12 mm, a detection efficiency of up to 40% and a time-resolution in the order of tens of ns.